Carrier-wave signaling system



Feb. 7, 1928. 1,658,337

J. s. JAMMER CARRIER WAVE SIGNALING SYSTEM 'Filed June 21. 1924 s sheets-sneer 1 o.

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J. S. JAMMER CARRIER WAVE SIGNALING SYSTEM Filed June 2l. 1924 3 Sheets-Sheet. 2

Feb. 7, 1928.

1,658,337 J. s. JAMMER CARRIER WAVE SIGNALING SYSTEU Filed June 21. 1924 s sneeze-snee: s HWF A.) HPOF g K R :d Man A R Ja ,q /0 Q u Mar. fj

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Repeaer LPOF Q2 LPIF Patented Feb. 7, 1928.

UNITED STATES JACOB S. JAMMER, OF NEW YORK, N. Y.. PANY, INCORPORATED, OF NEW YORK,

ASSIGNOR TO WESTERN ELECTRIC COM- N. Y., A CORPORATION OF NEW YORK.

CARRIER-WAVE SIGNALING SYSTEM.

Application tiled .Tune 21,

This invention relates to carrier wave signaling systems, and particularly to means for monitoring and talking over such systems at intermediate stations.

An object of the invention is to provide means for monitoring and talking over any channel of a carrier wave signaling system.

A related object of the invention is to facilitate the operation and maintenance of such a system.

A particular advantage of the invention is that it may readily be applied to a standard carrier wave signaling system without otherwise altering the system.

The invention provides means for monitoring and talking on any channel of a carrier system at repeater stations, the carrier current being selected from the line by means of band filters which may be connected across the output of the repeater amplifiers, this current being utilized to permit the repeater attendant to listen in on the carrier channels or to use any channel as a talking circuit to other stations.

The inventionwill be described as applied to a multiplex carrier current telephone system, although it will be understood that it may also be applied to other signaling systenis.

In the drawings:

Fig. 1 is a diagrammatic view illustrating a terminal station of a carrier telephone system.

Fig. 2 is a diagrammatic View of a carrier telephone repeater station embodying the invention.

Fig. 3 is a diagrammatic View illustrating a modification of the system of Fig. 2.

Reference will first be made to Figs. 1 and 2, which, when placed side by side with Fig. l at the left, represent the west terminal station and a mid-line repeater of a carrier telephone system interconnected by the multiplex line ML.

The usual east terminal station, which is identical to the west terminal station .shown in Fig. 1 is omitted for the sake of simplifying the showing. A carrier telephone system of this type, including both west and east terminal stations, as well as an intermediate repeater station, is illustrated in Fig. 24 of an article entitled Carrier current telephony and telegraplrv by Me srs. Colpitts and Blackwell, published 1924. Serial N0. 721,387.

in the Transactions of the American Institute of Electrical Engineers, vol. Ll0, 1921.

The terminal apparatus at the west station comprises a plurality of transmitting channels TC1, T C2 and TC3 connected through a common transmitting circuit TL to the main line ML, and a plurality of receiving channels RC1, RC2 and RC3 connected through a common receiving circuit RL to the main line ML.

Carrier currents are utilized for transmission over the'line ML and are grouped as to their frequencies, the higher frequencies, as a group, being used for transmission from west to east and the lower frequencies, as a group, being used for transmission from east to west.

A high pass grouping filter HP is paired with a low pass grouping filter LP at the terminal stations. These filters serve to separate the directional groups of carrier waves to the respective terminal transmitting and receiving circuits. These filters and each of the other filters shown throughout the system may be designed in accordance with the principles set forth in the United States Patentto Campbell, No. 1,277,113, issued May 22, 1917. Specific types of both high and low pass filters are shown, for example, in Fig. 11 of the Campbell patent.

Low frequency lines L1, L2 and L3 which may be telephone lines or other types of signaling lines. are associated with channels TG1-RC1, TCg--RC2 and TG3-RC3 respectively, for simultaneous and independent communication over the line ML with corresponding similar lines at the east station (not shown).

T he low frequency lines are provided with balancing artificial lines or networks N1, N2 and N3, respectively, and with differential repeatin coils H1, H2 and H3. commonly known as ybrid coils, for enabling independent transmission in the two directions between the line and the high frequency terminal apparatus.

Transmitting channel TC1 includes a modulator M1 and a band filter TBFl. Similarly, transmitting channel TC2 includes a modulator M2 and a band filter TBFQ, while channel TC3 includes a modulator M3 and a band filter TBF3.

Receiving channel RC1 includes a demodulator D1 and a band filter RBFl. Similarly, channel RC2 includes a demodulator D2 and a band filter RBFZ, while channel RC3 includes a demodulator D3 and a band filter RBF3.

The modulators associated with the various transmitting channels throughout the system may be of any well knowrrtype, such as that disclosed in the United States patent to van der Bijl, No. 1,350,752, issued August 2i, 1920. The various demoilulators may be of the well known vacuum tube tector type shown in Fig. ai'. of the Colpitts and Blackwell article, supra.

The mid-line repeater illustrated in Fig. 2 is connected to the multiplex line ML intermediate the terminal stations in the usual manner shown in detail in Fig. 24 of the Colpitts and Blackwell article. This repeater may be of any suitable type, such as thatdisclosed in the United States Patent to Raibourn, No. 1,413,357, issued April 18, 1922.

The upper and lower branches of the repeater contain amplifiers A, and A2, re-

- spectively which may be of the highly evacuated three-element electron discharge type for amplifying the current supplied to the respective branches. The upper branch 1s for repeating currents from west to east and includes a high pass input filter HPIF and high pass output filter HPOF; and the lower branch for repeating currents from east to west includes a low pass input filter LPIF and a low pass output filter LPOF.

' For further details of the arrangement of repeater filters and amplifiers reference may be had to the Raibourn patent, supra.

The carriersystem outlined above is of the type inwhich the carrier current is transmitted continuously, as distinguished from the type in which the carrier is suppressed from transmission. A system of this general character is described in connection with Fig. 42 of the Colpitts and Blackwell article, supra.

In this system, carrier currents of the frequency assigned to channel TC, are supplied from a source O1 to the modulator M1 wherein they are modulated b voice frequency currents or other signaling currents from the low frequency line L1. Carrier source O2 and O3 of the other respective carrier frequencies are similarly associated with modulators M2 and M3, respectively.

The various band filters associated with the terminal transmitting and receiving channels are so designed that they will transmit bands of frequencies including the carrier assigned to the respective channels as well as one of the side bands, either the upper or lower as desired, and will suppress from transmission frequencies lying outside of such band.

Voice frequency currents originating, for instance, in the low frequency line Ll at the west st-ation pass through the associated hybrid coil H1 into the modulator M1 in the transmitting channel TG1. There is likewise fed into the modulator the carrier current from the oscillator C)1 as described above. Of the components of modulation appearing in the output circuit of the modulator L\I the transmitting band filter TBFl suppresses all except one side band, for eX- ample the upper side band. and the carrier, which it transmits or passes into the common transmitting circuit TL. The currents so transmitted from channel TC, and the other transn'iitting channels then pass through the high pass grouping filter HP to the multiplex line ML. The currents thus transmitted from the west station are selected by the repeater filter HPIF, are passed through the amplifier A, and thence through filter HPOF to the line ML. The incoming currents at the east station (not shown) are received in the same manner as incoming currents at the west station. For example, currents transmitted from the east station are picked up at the west sta-tion by the low pass grouping filter LP and are passed through the common receiving circuit RL and the respective receiving band filters RBF1, RBF2 or REFS, as the case may be. Currents transmitted through band filter RBF1,

for example, are demodulated in the demodulator D and the voice frequency components of demodulation appearing in receiving channel RC1 are transmitted through hybrid coil H, to the low frequency line L,.

As shown in Fig. 2, the inventiorprovides means whereby the attendant at titrepeater station may listen in on any carrie.V channel without interrupting the transmission of messages between the terminal stations. Means are also provided whereby the repeater attendant may use any channel of the system as a talking circuit to other stations.

A loop demodulater-modulator circuit LDM, is associated with a common transmitting and receiving circuit TRl through the balanced three-winding repeating or hybrid coil H4, the other side of which is connected to the balancing network N4.

The circuit LDMl comprises a receiving channel 5 and a transmittingr channel G made conjugate by the hybrid coil H,. The receiving channel 5 includes a demodulator 7, and the transmitting channel 6 includes a modulator 8. An operators set. comprising a transmitter T, receiver R and appropriate connections therefor, is associated with the output of the demodulator 7 and with the input of the modulator 8.

The circuit TR1 terminates in jacks J, and J2. A plurality of monitoring band filters MBFI, MBFQ, M1BF1 and M,BF2 are provided for separating a. desired channel to be used for monitoring or talking from the rest of the channels. The band filters MBFL and MBF2 are adapted to be associated with the circuit TR, by mean-s of plugs f) and l0, respectively. cooperating with the jack J1. Similarly, the band filters ,BF, and MLBF2 may be associated with the circuit TR1 by mean-s of plugs 11 and 12, respectively, cooperating with the jack J2. Channel taps terminating in one or more jacks J3, L and one or more jacks J' .Tw etc. are provided at the repeater station in the output circuits of amplifiers A1 and A2. respectively. Baud filters HBF, and MBF2 may be associated with jacks J3 and J4, respectively, by means of plugs 13 and 14, While band filters M11-3F, and LBF, may be associated with jacks J5 and Jh., respectively, by means of plugs l5 and 16.

It Will be understood that the band filters MBF1, MBF2, MlBF1 and H1131"2 are each designed to transmit frequencies of a range assigned to a particular channel of the system. For example, filter MBF1 will pass a frequency range identical to that assigned to transmitting band filter TBF1 alt the west terminal station, while hand filter MBF2 will pass frequencies of the range assigned to transmitting filter TBF2. Similarly, band filter M1BF1 passes frequencies of the range assigned to terminal filter RBF1 and band filter ELBF, pas-ies frequencies of the range assigned to terminal filter RBF2, and so forth.

If the repeater attendant desires to monitor on one of the channels, for example, on the channel associated with low frequency line L1. he will insert plugs 9 and 13 into jacks J1 and J3, `respectively, and Will also insert plugs 11 and 15 into jacks J2 and J5, respectively. This connects band filters MBF1 and MlBF1 across the output of amplifiers A1 and A2, respectively. The resistances R in circuit with the band filters MBF1 and MlBF1 offer a high impedance to the output currents of amplifiers A1 and A2 so as to introduce only a small loss and a resultant small change in the overall equivalent of the channel. The currents passing through filters MBF1 or BLBF, cannot pass to the opposite branch of the repeater circuit due to the fact that filter MBF1 does not pass frequencies of the range assigned to filter MIBFP and vice versa. The monitoring currents pass through the hybrid coil H4 to the receiving channel 5, and thence to the demodulator 7 Where they are demodulated, the voice frequency components being heard in the attendants telephone receiver R, and the high frequency wave components passing through modulator 8, hybrid coil H4. circuit TR,. and back through the respective filters MBFl and MlBFl to the line.

When the repeater attendant desires to talk to another station, he operates key K in circuit with the band filters MBF1 and M,BF,. thus removing the resistances R from the circuit and allowing more carrier current to pass into the demodulator 7. This introduces a greater loss in the channel output to the line, but this loss is compensated for by the regenerative gain introduced by the loop demodulator and modulator hybrid circuit LDMl. The currents passing through band filters MBFI and A\[,BF1 to thc demodulator 7 are demodulated, the voice frequency components being heard as before in the attendants telephone receiver R, and the carrier components passing on to the modulator 8 Where they are modulated by the voice frequency currents from the attendants transmitter T. The currents so modulated are passed through the hybrid coil H4 to the circuit TR, and thence through the particular band filter MBF1 or MlBF1 designed to pass currents of those frequencies. It will thus be seen that when the attendant talks, the sideband currents are tran-smitted to both the east line and the West line and the attendant is able to talk to other repeaters or to either terminal station.

A modification of the invention is shown in Fig. 3, which illustrates a line repeater of a carrier telephone system in which the carrier is suppressed from transmission.

In a carrier system of this type the carrier Wave of each channel is suppressed from transmission when no signals are being sent. and When signals are being transmitted the 10 modulation components of the modulated wave are sent over the line, but no un1nodu lated components of the carrier Wave are transmitted. In order to reproduce the signal from modulated Waves of this character, 105 it is necessary that a carrier Wave of substantially the same frequency as that suppressed at the transmitter should be supplied to the demodulator atthe receiver. A system of this general character is described in connec- 110 tion with Fig. h19 of the Colpitts and Blackwell article, supra. The terminal stations associated with the opposite ends of the multiplex line ML of Fig. 3 may be identical with that shown in Fig. 1 except that oscilla- 115 tors should be associated with the demodulators D,. D2, etc., in the saine manner in which oscillators 0 O2, etc. are associated with modulators M1, M2, etc., and the modulators employed at the terminal stations should be 120 of the balanced type shown in Fig. 49 of' the Colpitts and Blackwell article. These balanced modulators, which are employed `for the purpose of suppressing the carrier from transmission may be of the specific type 125 shown in the U. S. patent to Carson, No. 1.343306, issued June 15. 1920.

Since, in the carrier suppression system the carrier is suppressed at the terminal station, means are provided at the repeater sta- 13C both the modulator and the demodulator ot'V the monitoring circuit. For this purpose a double frequency oscillator is used. This oscillator is designed to generate simultaneously the tivo carriers required for east and West transmissions.

The loop demodulator-modulator circuit L'DM.: of Fig. 3 comprises a receiving channel 20 and a transmitting channel 2l which are made conjugate by means of a hybrid coil H5, one end ot' which is' connected to thc common transmitting and receiving circuit TR2 and the other end of which is connected to a balancing network N5. The receiving channel 20 includes the demodulator 22 the output circuit of which is coupled to the attendants receiver R. The transn'iitting channel 21 includes the balanced modulator 23 the output circuit of which is coupled through the lowfrequeney circuit 21 to the attendants transmitter T. The hybrid coil H5 prevents excessive side tone in the attendants receiver. The modulator 23 is of the balanced type disclosed in the Carson patent. supra, designed to prevent the passage of the carrier current to the line.

The demodulator 22 and the modulator 23 are rendered conjugate by means of a hybrid coil HG thus preventing singing at the repeater. The double frequency oscillator 25 is coupled to the hybrid coil H6, by means of the transformer 26, the balancing network Nli being connected to the other side of the hybrid coil.

The double frequency oscillator 25 may be adjusted by means of variable condensers 27 and 28 to generate simultaneously the two carrier Waves off'any desired frequency which are required forieast and West transmissions.

In describing the operation of the system of Fig. 3, it may be assumed that the repeater attendant desires to monitor and talk on channel No. 2, similar to the transmitting and receiving channel associated with the low frequency line L2 of Fig. 1. In this case the attendant inserts plugs 10 and 14 into jacks J, and J 4, respectively, and inserts plugs 12 and 16 into jacks J2 and J6, respectively. The sideband transmitted from the west station passes through the repeater directional filter HPIF amplifier A, and filter I-lIOF to the line ML. and thence to the cast station. A portion of such sideband in the output of amplifier A, passes through jack J plug 14, resistances R, band filter MBFQ, plug 10, jack J1, circuit TR2, through the hybrid coil H5, receiving channel 20 to the demodulator 22. There is likewise fed into the demodulator 22 a carrier currentof a frequency equal to that suppressed at the transmitting terminal, from the double frequency oscillator 25 the variable condenser 27 of which may be assumed to be adjusted to cause the generation of that particular frequency. The voice currents transmitted lfrom the west station appear in the receiver- R- as one of the components of demodulation, Similarly, a portion of the incoming sideband from the east station passes from the output side of repeater A2 through band filter BLBF: to the demodulator 22 where it is combined with a carrier current of a frequency equal to that suppressed at the transmitting terminal, which carrier is supplied oy the double frequency oscillator 25 the variable condenser of which is adjusted to cause the generation of that particular frequency. l

'hen the repeater attendant desires t0 tall( to another station, the voice frequency currents from the transmitter T are impressed upon the input circuit of the. balanced modulator 23 and are caused to modulate the carrier currents which are fed to the modulator 'from the double frequency oscillator 25. The carrier currents are balanced out in the modulator 23 and the side bands are transmitted through the hybrid coil H5 and the band filters MB1?2 and MlBF2 and out on the carrier line. Hence, when the repeater attendant talks the Sideband currents are transmitted to both the east line and the west line and the attendant is able to talk to other repeaters or to either terminal station.

IVhen it is desired to monitor and talk on any other channel on the system, the appropriate monitoring band filters are associated with the channel taps in the output circuits of amplifiers A, and A2 and the condensers 27 and 28 are so adjusted that the double frequency oscillator 25 will generate simultaneously the two carriers appropriate to the east and westtransmissions of the selected channel.

The invention set forth herein is, of course, susceptible of various modifications and adaptations. and accordingly the invention is not to be considered as limited except as defined by the scope of the appended claims.

Vhatis claimed is:

1. In a carrier Wave signaling system, a multiplex carrier line employing carrier Waves of different frequencies for carrying messages. a. repeater associated with said line and including a Wave filter having a plurality' of sections and an amplifier dividing said sections into two groups. a monitoring circuit, a plurality of selective paths associated with said repeater between the output of said amplifier and one of said filter groups, each 0f said paths being select-ive to a different one of said carrier Waves, and means for selectively associating said monitoring circuit with a desired one of said selective pat-hs.

2. In a carrier Wave signalin system, a multiplex carrier line employing carrier waves of different frequencies, a repeater associated with said line, means at said repeater for selecting a wave from said liuc, means for observing the selected wave. and means for retransmitting said wa re through said selecting means.

3. In a carrier wave signaling system. a multiplex carrier line employing carrier waves of different frequencies, a repeater associated with said line. channel taps at said repeater'. means adapt-:ld to be associted with said channel taps for selecting a wave from one of the carrier channels, means for detecting the selected ware and means for retransmitting said wave through said selecting means.

4. In a carrier wavev signaling system, a multiplex carrier line employing carrier waves of different frequencies. a repeater associated with said line, a channel tap at said repeater. a band filter associated with said channel tap for selecting a wave from said line, means for detecting a wave selected by said band filter, and means for retransmitting said wave through said band filter.

5. In a carrier wave signalingr system, a multiplex carrier line employing carrier Waves of different frequencies, a repeater including an amplifier associated with said line, a channel tap in the output of said amplier, a band filter associated with said channel tap for selecting a wave from said line, means for detecting a wave selected by said band filter, and means for retransmitting said wave through said band filter.

6. In a carrier wave signaling system. a. multiplex carrier line employing carrier waves of different frequencies, a repeater associated with said line, a channel tap at said repeater, a band filter associated with said channel tap for selecting a wave from said line, a detector for the wave selected by said band filter for deriving the signal component and the high frequency wave component, and means for retransmitting the high frequency wave component controlled by other signals through said band filter.

7. In a carrier wave signaling system, a multiplex carrier line employing carrier Waves of different frequencies, a repeater associated with said line and including a Wave filter having a plurality of sections and an amplifier dividing said sections into two groups, a channel tap in the output of said repeater amplifier, a band filter associated with said channel tap for selecting a Wave from said line, a detector for the Wave selected by said band filter for deriving the signal component and the high frequency wave component, and means for retransmitting the high frequency wave component con- ;ixolled by other signals through said band ter.

8. In a carrier wave signaling system, a multiplex carrier line employing carrier wares of different frequencies for oppositely directed transmissions, a repeater associated with said line, channel taps at said repeater. :i loop monitoring circuit having a common input` and output circuit, band tilters associated with said channel taps, switching means for connecting said common input and output circuit to each of two hand filters associated with oppositely directed channels, and means in said loop monitoring circuit for detecting a wave transmitted through one of said band filters and for rctransmitting said wave through the same band filter.

9. In a carrier ware signaling system, a multiplex carrier line employing carrier waves ot' different frequencies for oppositely directed transmissions, a repeater associated with said line, channel taps at said repeater, a loop monitoring circuit having a common input and output circuit, band filters associated 'with Asaid channel taps, switching means for connecting said common input and output circuit to each of two band filters associated with oppositely directed channels, a demodulator in said loop monitoring circuit for deriving the signal component and the high frequency component of a wave transmitted through one of said band filters, a telephone receiver in the output of said deniodulator for observing the detected signal, and means for retransmitting the high frequency wave component controlled by other signals through said last mentioned band filter.

l0. In a carrier wave signaling system, a multiplex carrier line emplo ing carrier waves of different frequencies or oppositely directed transmission, a repeater including amplifiers for amplifying the oppositely directed carrier waves, channel taps in the output circuits of said amplifiers, a loop monitoring circuit having a common input and output circuit, band filters associated with said channel taps, switching means for connecting said common input and output circuit to each of two band filters associated with oppositely directed channels, means in said loop monitoring circuit for detecting a wave transmitted through one of said band filters, and means for retransmitting said wave through the same filter.

l1. In a carrier Wave signaling system, a multiplex carrier line employing carrier waves of different frequencies for oppositely directed transmission, a repeater associated with said line and including a channel for repeating in one direction currents of one range of frequencies and a channel for repeating in the other direction a band of currents outside of said range of frequencies, each channel comprising a band filter consisting of two groups of recurring sections and an amplifier electrically interposed between said groups, channel taps in the output circuits ot' said amplifiers, a loop monitoring circuit having a common input and output circuit, band filters associated with said channel taps, switching means for connecting said common input and output circuit to each of two band filters associated with oppositely directed channels, and means in said loop monitoring circuit for detecting a wave transmitted through one of said band filters and for retransmitting said wave through the same filter. l

12. In a carrier wave telephone system, a multiplex carrier line employing carrier Waves of different frequencies for transmitting messages in opposite directions, a two- Yway repeater comprising band filters, each of which consists ot' two groups of recurring sections for separating the oppositely directed messages and amplifiers, respectively, positioned between the groups of filter sections, a monitoring circuit, selective filters, and means for connecting said monitoring circuit through the selective filters to the output circuits of said amplifiers whereby monitoring may be effected on the messages transmitted in either direction and whereby conversation may be effected from the repeater with another station.

In witness whereof, I hereunto subscribe my name this 12th day of June A. D., 1924.

JACOB S. JAMMER. 

